Getting the start at first base, Realmuto presented the biggest problem of the day for Stephen Strasburg, who was on point and threw his first shutout of the season and the second of his career.
Realmuto doubled in the second inning and led off the fifth with a triple down the left-field line. It was a key moment during a scoreless game. Strasburg worked out of it with consecutive strikeouts and a flyout to left.
In the seventh inning, Realmuto singled, leaving only the home run. He had one more chance in the ninth, but he grounded out to short.
As an organization, the Marlins have two World Series titles, and six pitchers have thrown no-hitters. But the cycle has eluded the club.
"I've been one away four times in my career now but haven't gotten it yet," Realmuto said. "I was a triple away once. A double away once and a homer away once. I can't remember the other one."
The Marlins managed just six hits on the day, and they were swept in the three-game set. They're back to .500 (66-66) with 30 games remaining. With Colorado's loss to Detroit, Miami remained 5 1/2 games back for the second National League Wild Card spot.
The Phillies visit Marlins Park for a four-game series beginning at 7:10 p.m. ET on Thursday.
"It kills us to not at least come out of here with one win," Realmuto said. "We really needed this one to get us back on our feet today. With [the Phillies] coming to town, we've got to take care of business there and get back on a roll."
For Realmuto, Wednesday was a day to get back on track. He had been in an 0-for-17 slide, including hitless in his eight at-bats in the first two games against the Nationals.
Marlins manager Don Mattingly is trying to keep Realmuto in the lineup and as fresh as possible. That's why, after catching on Monday and Tuesday, he played first base on Wednesday.
"It definitely helps me stay fresher than catching does," Realmuto said. "It's just nice to be able to get a breather and a little rest on my legs and still stay in the lineup."
The Marlins have been patching together first base with Justin Bour on the disabled list since July 25 with a right oblique strain.
Bour is close to going on a rehab assignment at Double-A Jacksonville, and he could return in a couple of weeks.
Realmuto gives Mattingly another option to go along with Tomas Telis and Tyler Moore at first. A.J. Ellis caught on Wednesday.
"It's just a matter of who you're choosing," Mattingly said. "If you're choosing J.T. at first, it means you're choosing A.J. over Teli or A.J. over Moore. Your choice is not necessarily J.T., it's who do you want for the other guys."